The invention relates generally to joist hangers and beam supports. More particularly, the invention relates to a joist hanger and beam support retrofit system.
There is a great need for stable and secure support of wooden framing members, in the form of wooden beams or joists, held within hardware designed to support such beams or joists. Typical examples of hardware designed to provide support are ‘post caps’ which attach the top of a post to a girder, or ‘joist hangers’ which attach joists for floors or decks to girders or walls. In addition to the support hardware, most wood framed structures require fasteners, in the form of nails or bolts, to connect different structural members. For example, these fasteners are inserted laterally through both the joist and joist hanger or beam and beam support. The fasteners are intended only to secure the joist and joist hanger or beam and beam support to each other and not intended to support the joist within the joist hanger or the beam within the beam support. In each case, the capacity of these fasteners or connectors is calculated by the shear strength of the nails or bolts required and the bearing capacity of the support hardware. The bearing capacity of the support hardware is determined by the area of the hardware the lumber rests upon and the compressive strength of the wood.
The basic assumption is that a bottom of the joist or beam rests upon a base plate, also referred to as the ‘seat’ or ‘saddle bottom’ of the hardware and is held in place by the fasteners. However, this is rarely seen in practical situations. Usually, a joist or beam made of wood shrinks after installation and a gap results between the plate of the hardware and the bottom of the wood member or beam the hardware is supposed to be supporting. As a result, the fasteners end up supporting the wood member. However, as discussed above, the fasteners were not designed to support the joists or beams and the bearing capacity of the hardware was not based solely on the fasteners.
This situation is common wherever one examines a wooden members or beam that has been in service for a year or two. Millions of wooden members have been installed over the decades, if not centuries, and many more are installed each day. Shrinkage cannot easily be controlled or accurately anticipated.
A conventional metal joist hanger 20 and wooden joist 22 are shown in FIGS. 1-4. When the joist 22 is initially placed within the joist hanger 20, the joist 22 rests within the joist hanger 20 and is supported on a base plate 24 of the joist hanger 20. Non-load bearing lateral fasteners 26 are used to secure the joist 22 in the joist hanger 20. With reference to FIGS. 3 and 4, the joist 22 and the joist hanger 20, are shown after a gap or space 28 is formed between the base plate 24 and the joist 22. The space 28 results from shrinkage of the wood forming the joist 22 over a period of time, thus causing relative movement of the base plate 24 and the joist 22 over time. This causes a load to be placed upon the fasteners 26 for which they were not designed.
Many different types of joist hangers have been employed to support beams. However, such systems use screw assemblies to adjust the location of the supporting plate of the joist hanger. For example, U.S. Pat. No. 4,192,623 discloses an adjustable joist hanger for supporting concrete decks. However, the screw assembly disclosed therein is intended to allow assembly and disassembly. In another example, U.S. Pat. No. 4,124,962 discloses a joist hanger for supporting beams that includes a screw assembly for changing the elevation of joists. However, the joist hanger lacks an integral saddle plate and the screw assembly disclosed therein is held in place by lateral fasteners which results in the lateral fasteners supporting both the screw assembly and the joist.
While methods such as those described above may provide means of providing support for beams, such methods can always be improved to provide better and more simplified means of providing support.
Accordingly, there is a need for relieving the stress upon lateral fasteners caused by the shrinkage of wood joists. What is also needed is method to retrofit conventional joist hangers. There is a further need for a means to provide additional support that compensates for the shrinkage of wood. There is an additional need for filling the gap caused by the shrinkage of wood that is relatively compact in size and inexpensive. The present invention satisfies these needs and provides other related advantages.